Project Summary/Abstract Idiopathic Pulmonary Fibrosis (IPF) is characterized by progressive fibrosis of the gas-exchange apparatus leading to either death by asphyxiation or lung transplant. Currently there are two approved therapies to slow the progression of IPF, but no therapies for halting the disease. Our work is focused on bridging the knowledge gap regarding the molecular mechanisms of IPF progression, a prerequisite for developing therapeutics that arrest the disease. Our lab, along with others in the field has identified a feed-forward loop in IPF. When lung fibroblasts sense the fibrotic extracellular matrix (ECM) in IPF there is downregulation of the microRNA biogenesis machinery component DICER1. This leads to decreased microRNA biogenesis, including the master negative regulator of ECM genes, miR-29; which in turn results in increased ECM deposition and progression of fibrosis. Expression of the DICER1 transcript is controlled post-transcriptionally through binding by the RNA-binding protein AU-rich element binding factor 1 (AUF1), leading to rapid mRNA decay. Our preliminary work has identified activation of the AUF1-DICER1 mRNA interaction in primary human lung fibroblasts on IPF-ECM, leading us to ?hypothesize that ECM-dependent modulation of AUF1 function is a major mechanism for DICER1 suppression and the development of a fibrogenic phenotype. In Aim 1, using primary human lung fibroblasts cultured on control ?versus IPF-ECM, we will decipher the AUF1-DICER1 mRNA interaction followed by a genome wide-assessment of the AUF1 interactome. In aim 2, we test the hypothesis that AUF1 modulation is sufficient to confer a fibrotic phenotype on an otherwise normal primary human lung fibroblast using two xenograft models: 1) Gain and loss of AUF1 function in our previously published zebrafish embryo xenograft model and 2) Gain of AUF1 function in a mouse xenograft model. Through completion of these experiments under the mentorship of Dr. Peter Bitterman, and the training plan outlined in the attached documents, I will be well prepared to pursue the next steps toward a career as an independent pediatric physician-scientist.